The Clinical Picture

Aleukemic leukemia cutis

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Figure 1. The firm, indurated nodules ranged in size from 1 to 4 cm.

Figure 1. The firm, indurated nodules ranged in size from 1 to 4 cm.

An 85-year-old man presented with a 2-week history of rapidly progressive nodules on the scalp, neck, trunk, and extremities (Figure 1). He denied fever, weight loss, anorexia, night sweats, pruritus, or pain, and he had not started any new medications.

On examination, the numerous firm, indurated nodules ranged in size from 1 to 4 cm. There was no palpable lymphadenopathy.

Results of a peripheral blood cell count showed the following:

  • Hemoglobin 12.5 g/dL (reference range 13.0–17.0)
  • Platelet count 154 × 109/L (130–400)
  • White blood cell count 5.0 × 109/L (4.0–11.0)
  • Neutrophils 1.7 × 109/L (1.5–8.0)
  • Lymphocytes 2.2 × 109/L (1.0–4.0)
  • Monocytes 1.0 × 109/L (0.2–1.0)
  • Eosinophils 0 (0–0.4)
  • Basophils 0 (0–0.2)
  • Blasts 0.
Figure 2. Punch biopsy showed diffuse atypical cellular infiltrate in the dermis, with a grenz zone of uninvolved papillary dermis.

Figure 2. Punch biopsy showed diffuse atypical cellular infiltrate in the dermis, with a grenz zone (red arrow) of uninvolved papillary dermis (hematoxylin and eosin, × 10).

Punch biopsy study of the skin (Figure 2), showed diffuse atypical cellular infiltrate in the dermis, sparing the epidermis, with a distinct grenz zone, a narrow band of uninvolved papillary dermis between the neoplastic process and the uninvolved epidermis. The tumor cells were large, with ample, vacuolated cytoplasm, large blastic nuclei with irregular nuclear membranes, and abundant mitotic figures (Figure 3). The cells were arranged in a diffuse sheet, without glandular, squamous, or adnexal differentiation. They did not demonstrate pigment, which would have suggested melanoma. There was no lymphoid follicle formation.
Figure 3. The tumor cells were large, with ample, vacuolated cytoplasm, large blastic nuclei with irregular nuclear membranes, and abundant mitotic figures.

Figure 3. The tumor cells were large, with ample, vacuolated cytoplasm, large blastic nuclei (blue arrow) with irregular nuclear membranes, and abundant mitotic figures (red arrow) (hematoxylin and eosin, × 40).

Immunohistochemistry study demonstrated that the cells co-expressed T-cell markers (CD4 and CD43) and monocyte markers (CD68 and lysozyme). CD30 and ALK-1 were not expressed, ruling out primary cutaneous CD30 T-cell lymphoproliferative disorders and anaplastic large-cell lymphoma. CD2 and CD3 are typically expressed in mycosis fungoides, but these were not expressed. The tumor cells did not express myeloperoxidase, a myeloid marker.

The findings were consistent with leukemic cells with monocytic differentiation. The infiltrate was unusual because leukemic infiltrates typically demonstrate a high nuclear-to-cytoplasmic ratio, but in this case the malignant cells had moderate amounts of cytoplasm due to the monocytic differentiation. Also, a grenz zone is more typically seen in B-cell lymphomas, and T cells more typically demonstrate epidermotropism.

Bone marrow aspiration was performed and revealed a hypercellular bone marrow with trilineage maturation with only 2% blasts. The fluorescence in situ hybridization testing for myelodysplastic syndrome and acute myeloid leukemia was normal. A diagnosis of aleukemic leukemia cutis was made.

After 2 months of chemotherapy with azacitidine, the nodules were less indurated. Treatment was briefly withdrawn due to the development of acute pneumonia, leading to a rapid progression of cutaneous involvement. Despite restarting chemotherapy, the patient died.

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